(1) The most striking thing is how much of an outlier the US is in terms of GDP devoted to healthcare. Mandatory spending at 8.5% of GDP is similar to other countries. But then "voluntary" spending is an additional 8.8%, similar to most other countries total spending.
Probably this is an indication on something rotten with healthcare in the US. But the benign explanation might be that other countries seem to have limits on how much demand you can have for healthcare (for instance banning private insurance). So if demand weren't capped maybe other countries would increase healthcare spending.
In anycase, it makes the claim that Warren's plan would be bankrupt the system less creditable. Other countries spend much less on medical care.
(2) Many countries have not settled on single payer and still have universal coverage. eg Australia and France have duel payer systems. Germany, Switzerland and the Netherlands have competing payer. That indicates that reforming Obamacare is a viable way to achieve a steady state policy.
It looks like the main tradeoff is you end up with much higher rate times and reduced specialist services in single payer (eg 20+% in the UK/Can can't see a specialist in 2 months as opposed <10% in competing payer). But competing payer has endless wrangling over how to adjust risk pools and shared costs. Note this is on a sample of only two single payer systems.
It could be that given how lobbying works in the US the US would be particularly bad at single payer. Or maybe countries that join the game later are single payer because they can skip more pre-modern organizations of insurance.
At least from Switzerland it looks like not banning private insurance causes healthy competition with public insurance that improves the coverage of public insurance.
(3) No other country is completely free. They all have some level of copays and deductibles with subsidies for low income. Even the UK has 2% of GDP from voluntery spending including drug copays.
The anglosphere seems to fund healthcare through general taxation. Switzerland through premiums. And the other countries sampled through payroll taxes.
So Medicare-for-All is a bit of an outlier in that its neither funded by payroll tax and has no voluntery spending. It looks like an extreme version of the UK's single payer system.